Apparatus for repetitively unstacking blocks of sheet material



March 23, 1965 c. R. STEVENS 3,174,633

APPARATUS FOR REPETITIVELY UNSTACKING BLOCKS OF SHEET MATERIAL Filed Jan. 11, 1961 3 Sheets-Sheet 1 INVENTOR.

CHARLES R. STEVENS Manda/m ATTOR NEYS March 23, 1965 c. R. STEVENS 3,174,633

APPARATUS F OR REPETITIVELY UNSTACKING BLOCKS OF SHEET MATERIAL Filed Jan. 11, 1961 5 Sheets-Sheet 2 IN VEN TOR.

CHARLES R. STEVENS AT TORNEYS March 23, 1965 c. R. STEVENS 3,174,533

APPAfiATUS FOR REPETITIVELY UNSTACKING BLOCKS OF SHEET MATERIAL Filed Jan. 11. 1961 5 Sheets-Sheet 5 INVENTOR. CHARLES R. STEVE-NS AT'T'O RN ELYS United States Patent i 3 174,633 APPARATUS FUR RElETITEVELY UNTACKING BLOCKS 0F SHEET MATERIAL Charles R. Stevens, 4931 Oak Ridge Drive, Toledo, Ohio Filed Jan. 11, 1961, Ser. No. 81,999 7 Claims. (Cl. 214-85) This invention relates to an apparatus for unstacking blocks of sheet material each consisting of a large number of pieces, such as sheets of paper, and for the delivery of such blocks of sheets to subsequent sheet handling apparatuses or mechanisms such as, for example, an edge trimmer.

In the finishing rooms of paper mills, for example, sheets of paper are rough-cut to approximate size and stacked in high piles of many thousands, usually upon skids or similar carrying devices. The stacks of paper sheets often are divided by inserting indicators between adjacent groups of five hundred sheets each, so that in subsequent operations the operators can quickly tell how many sheets there are in a stack or in a block which may consist of a definite number, such as two, three, four or more groups.

In finishing rooms it is often necessary that blocks of sheets be unstacked from such stacks and delivered to other machinery such as the mentioned trimmer, which has a capacity of several groups, say two thousand individual sheets, and which accurately trims an edge of such a block of sheets at each stroke.

In the past these blocks of sheets have usually been manually separated and lifted ofi of a stack of sheets and manually inserted into the trimmer. This frequently resulted in cracks and scuffs on the sheets of paper, and in the sheets being dirtied by grease and dirt on the hands of the operators, and at best was exhausting and slow.

It is therefore the principal object of the instant invention to provide an apparatus which receives and supports a stack of sheets of material, for example a skid load, which moves the skid load upwardly in steps corresponding to the height of each block of sheets to be unstacked and which has a Simple, positive pusher for engaging a block of sheets and unstacking them, delivering such blocks of sheets off of the stack and onto a table and thence to subsequent sheet handling apparatuses such as the trimmer.

It is another object of the instant invention to provide an apparatus having a control means which includes an adjustable member for limiting the upward movement of the stack of sheets to steps each equal to the height of a block of sheets to be unstacked so that after each such block of sheets is unstacked, the apparatus moves the stack upwardly a distance such that the bottom of a subsequent block is aligned with the table across which it is to be moved as it is unstacked.

It is still another object of the instant invention to provide an unstacker including a block engaging member which automatically compensates for uneven surfaces of the block and of the top of the remaining stack beneath the block and across the upper sheet of which the block is slid as it is unstacked.

Yet another object of the instant invention is to provide an apparatus for unstacking blocks of sheets having an efiicient and improved separator means for pneumatically separating each block to be unstacked from the remainder of the stack of sheets.

Yet another object of the instant invention is to provide a pusher mechanism for an unstacking machine which is adapted to gently engage the edges of the blocks to be unstacked in such manner as to obviate the crimping or damaging of the sheets and yet firmly and with 3,174,533 Patented Mar. 23, 1965 apparatus embodying the invention shown in rest posi-' tion between unstacking cycles;

FIG. 2 is an enlarged, fragmentary, detailed view of a pusher mechanism engaged with the edge of a block of sheets shortly after initial engagement thereof;

FIG. 3 is a fragmentary view in elevation similar to FIG. 1 but shown on an enlarged scale and illustrating the mechanism at a position in an unstacking cycle subsequent to the position shown in FIG. 2;

FIG. 4 is a fragmentary horizontal sectional view taken along the lines 44 of FIG. 2;

FIG. 5 is a fragmentary view in elevation similar to FIG. 2 but showing the pusher mechanism engaged with the edge of a block of sheets wherein the thickness of the sheets varies and the top surface of the remainder of the stack of sheets is therefore non-planar and illustrating how an apparatus embodying the invention automatically accommodates itself to such conditions;

FIG. 6 is a fragmentary view in elevation of an improved stack separator with which the machine embodying the invention is equipped, and

FIG, 7 is a diagrammatic view of a hydraulic system and control embodying the teachings of this invention,

Apparatus embodying the invention comprises a number of major sub-assemblies including a horizontal table generally indicated at 10 which is mounted on the top of a support pedestal 11, an elevator generally indicated at 12, a control 13 for the elevator 12, a horizontal guideway generally indicated at 14 which extends across the elevator'lZ from that side of the elevator 12 remote from the table It and to the table 10, a stack separator gen erally indicated at 15 and a pusher mechanism generally indicated at 16 which is reciprocable along the guideway 14.

The table 10 has a horizontal surface supported by the pedestal 11 at a level above the floor 17 of the plant in which the apparatus is employed. The table 10 includes a fixed portion 18, a horizontally movable portion 19 and a tiltable portion 20. The tiltable portion 20 bridges a space between the table 16 and an adjacent mechanism or apparatus such as a trimmer, fragmentarily indicated at 21 and having a vertically reciprocal trimming knife 22.

The elevator 12 is movable from a lowermost position with its top surface 23 at the level of the floor 17 to an uppermost position where the surface of a skid 24 is slightly above the horizontal level of the table 10 to provide for the discharge of the lowermost block of sheets in a stack 25 carried by the skid 24 on the elevator 12. The stack 25 comprises a plurality of superposed groups 26 each of which consists of a fixed number of sheets, for example 500, and between adjacent ones of which are inserted indicator slips 27. A block of sheets may consist of one or more groups 26 and, in the illustrated embodiment of the invention, each block 28 consists of three groups 26.

The purpose of an apparatus embodying the invention is to unstack successive blocks 28 of sheets off of the top of a stack 25 delivering each such'block 28 across the table 10 and -to the subsequent apparatus such as the trimmer 21. To this end the apparatus also includes the horizontal guide-way 14 which is illustrated as comprising a horizontal overhead track 29 supported upon pillars 30 and extending across above the elevator 12 and stack 25 thereon from the side of the elevator 12 remote from the table 10 to the table 10. The track 29 guides and supports .a carriage 31 of the pusher mechanism 16 and mounts a horizontal pneumatic cylinder 32, the piston rod 33 of which is connected to the carriage 31. By alternately admitting air into the two ends of the cylinder 32 the piston rod 33 and the carriage 31 of the pusher 16 are'recipr'ocated back and forth across the track 29.

. The pusher mechanism 16 comprises, its main carriage 31 and a pair of downwardly extending parallel guide angles 34 (see also FIG. 4) which are rigidly connected td each other by a cross rod 35 which also functions as a mounting bar for the lower end of a pneumatic cylinder 36. Aslide 37 is guided for vertical movement on the guide angles 34 by rollers 38 and the slide 37 pivotally mountsa pusher frame 39 for movement between an angular po's'ition (FIG. 1) and a vertical position (FIGS. 2, 3 and 5); The pusher frame 39 is mounted by a pair of outwardly extending pivot pins 40 (FIG. 4) and also come prises an upper crossbar 41.

A vertical pusher plate 42 and a right angle plate 43 are both adjustably supported on the pusher frame 39 and heldin adjusted position by a locking shaft 44 which extends through vertical slots (not shown) in the plates 42 and 43 and is threaded into the crossbar 45 of the pusher frame 39.

The vertical positions of the pusher plate 42 and the right angle plate 43 are adjustable relative to the pusher frame 39 so that when the horizontal web of the right angle plate 43 rests upon the uppermost sheet of the block of sheets 28 (see FIG. 2), that part of the vertical pusher plate 42 which extends downwardly beyond the horizontal web of the right angle plate 43, has a length slightly less than the height of the block 28 to be separatedv The position of the vertical pusher plate 42 and right angle plate 43 on the pusher frame 39 is also adjustable sothat when the pusher frame 39 is tilted forward (FIG. 1), the angle between the plates 42 and 43 is approximately aligned with the upper corner of the block of sheets 28 to be separated. V

The cylinder36 has a rod 46the end of which is pivotally coupled to the rear end of an arm 47, which is secured to and extends rearwardly from the crossbar 41 of the pusher frame 39. Two similar arms 48 extend forwardly froni the crossbar 41 and coil springs 49 and are engaged between the ends of the arms-48 and catch fingers 49a extending outwardly from the upper ends of the side members of theslide 37. The springs 49, acting through the arm 48, tend to swing the pusher frame 39 on its pivot pins 40 to the position shown in FIG. 1. Conversely, when air is admitted to the cylinder 36, the rod 46 is extended, which-acting through the arm 47, swings the pusher frame 39 ton vertical position and then, upon further extension, pushes the entire slide 37 upwardly along the: guide angles 34. A

At the po sition shown in solid lines in FIG. 1, both ends of the cylinder 36 are vented to atmosphere so that the slide 37 has moved down the guide angles 34 under force of gravity to its lowermost position. When the cylinder 32is activated to draw its rod 33 inwardly and to move the carriage 31 and pusher mechanism 16, the right angle plate 43 firstengages the upper outer corner of the upper most block of sheets28 and,as the pusher mechanism 16 continues to move, the frame 39 tilts on its pivot pins 40 against the spring 49 and subsequent engagement of the right angleplate 43 with the uppermost sheet of the block of sheets 28 exerts a cam action to move the slide 37 upwardly. The position of the pusher frame following en- 'gag'ement just described is. illustrated in FIG. 2.

, Control switches 50 (FIG. 1) 51 and 52 (FIGS. 1 and '3) control the direction and speed of movement of the pusher mechanism 16, beingengaged by parts of the carriage 31 at the ends of the stroke to reverse the pneumatic connection to the power cylinder 32 and, with respect to the switch 51, to open a metering valve on the exhaust side of the cylinder 32 during a forward stroke When the pusher mechanism 16 is pushing a block 28 on of the stack 25, in order to speed up the stroke at this point (FIG. 3) so that the remainder of the forward travel of the pusher 16 is at a higher rate of speed. This gives suflicient momentum to the stack so that it is projected across the tiltahle table portion 29 beyond the point to which it is moved when the pusher 16 reaches the limit'of its travel as determined by its switch 52;

Referring to FIGURE 7 there is shown in greater detail the means for accelerating the rate of movement of said pusher 1s and said block 28 at a selected point in the travel thereof. A hydraulic system is utilized having a pump 70, a reversing valve 71, and conduits 72 and 73 connecting suitable ports of the reversing valve 71 to the hydraulic cylinder 32 on opposite sides of the piston 80. As is well known When pump 70 is running, with the sliding portion of the reversing valve 71 in the position shown in a solid line, fluid is forced through conduit 72 to push the piston to the left in the drawing, while fluid is exhausted through conduit 73 to the reservoir 76 and V the return conduit 77 to be reused by pump 71). Conversely, when the sliding portion of the reversing valve 71 is in the position indicated by the dotted line, fluid is forced through conduit 73 to push the piston to the right in the drawing, while fluid is exhausted through conduit 72 to the reservoir 76.

In order to provide the acceleration of the rate of movement of the pusher 16 to the left in the drawing, parallelconduits 73a and 7312 are connected in conduit 73. Conduit 73b has a check valve 75 therein allowing free flow of fluid to cylinder 32 when pump- 7%) is forcing piston80 to the right, but no flow through parallel conduit 73b when the piston is moving to the left. Thus flow must be through a metering valve 74 or other variable resistance means connected in parallel conduit 73a when the piston 80 is moving to the left. Before carriage 31 actuates switch 51 flow is reduced through metering valve 74. Actuation of switch 51 provides a signal through leads 90, 91 to the electrically controlled metering valve 74. In response to this signal, valve 74 allows greater flow therethrough and thus a faster rate of travel by carriage 31 and pusher 16. Switch 51 is deactuated on the return trip of carriage 31 and metering valve 74 returns to its preset or initial position.

When the carriage 31 closes the switch 52 it reversesthe connection to the power cylinder 32 and also admits air to the lower end of the pusher mechanism cylinder 36. This extends the cylinder rod 46 swinging the pusher frame 39 to vertical position and moves the slide 37 to the upper position (shown in dotted lines in FIG. 1) so that during the return stroke of the pusher mechanism 16' all of its parts are elevated well above the uppermost portion of the stack 25 from which the block 28 has just previously been removed. When the carriage 31 reaches the rearmost position and engages the switch 50, air is cut off from the pneumatic cylinder 32 and the pusher mechanism cylinder 36'is vented allowing the spring 49 to again swing the pusher frame 39 to its angular position and allow the slide 37 to move downwardly under the force of gravity to its lower position.

At the time of initial engagement of the right angle plate 43 and vertical pusher plate 42 with the uppermost corner of the block of sheets 28, the resiliency of the spring 49 cushions the shock preventing damage to the edges of the sheets of paper and, particularly, preventing shuffling of the sheets of paper in the separation plane. During the extension of the spring 49 in this initial engagement of the pusher mechanism 16 with the block of sheets 28, the pneumatic power means 32 builds up pressure and overcomes the inertia of the block of sheets so as tomove it away from rest position with a firm yet steady rate to" cooperate in avoiding the damage and shutlling which is described.

Apparatus embodying the invention also includes the elevator control 13 which comprises a switch actuator 53 dependingly mounted from a switch 54 that is mounted on the end of a bent switch bar 55. The bar 55 overhangs the edge of the stack 25 of sheets and is vertically slideable in a clamp 56 mounted upon the table pedestal 11. By loosening the clamp 56 an operator may move the switch bar 55 vertically so that the actuator 53 hangs down to a level spaced above the horizontal plane of the table a distance which is slightly greater than the height of a block 28 to be separated. The power mechanism of the elevator 23 lifts the skid 24 and stack 25 vertically until the uppermost sheet of the stack 25 engages the switch actuator 53 which opens the control switch 54 to stop the elevator.

\Vhen the skid 25 is initially placed on the elevator 23 the operator actuates the correct one of a plurality of control buttons 57 to move the horizontally movable table portion 19 over near to the edge of the stack 25 and then' actuates the elevator mechanism to lift the stack 25 until the bottom edge of a block 28 is just above the level of table 10. He then loosens the clamp 56 and adjusts the vertical posit-ion of the switch 54 until the actuator 53 engages the topmost sheet of the block 28 with sufficient force to actuate the switch 54. Thereafter each subsequent cycle includes the movement of the elevator 23 upwardly in a step equal to the height of a block 28 determined by the engagement of the upper sheet thereof with the switch actuator 53.

The apparatus embodying the invention also includes a separator means which is insertable between the lowermost sheet of a block 28 to be unstacked and the uppermost sheet of the remainder of the stack 25. The separator means 15 is illustrated in FIG. 6 and comprises a nozzle 57 clamped on the end of an air hose 58 leading from a source of air under relatively low pressure. The nozzle 57 consists of two pieces of tightly woven, heavy fabric 59 and 60 which are stitched together along their longitudinal edges forming a fabric tube having fiat margins and an open end. Preferably the tightly woven fabric pieces 59 and 60 are thick enough so as to be quite stiff in a direction transverse to their length, quite flexible lengthwise and with tight enough weave so that air flows only slowly through the surface of the fabric pieces 59 and 60. When an operator inserts the separator means 15 between the block 28 and the stack 25 and air is discharged therethrough, the ends of the two fabric pieces 59 and 60 separate slightly, allowing the major portion of the air under pressure to flow out of the open end of the nozzle 57 with lesser air flow exuding through the fabric pieces 59 and 60. The flow of air between the two sheets of paper at the bottom of the block 28 and top of the stack 25 separates these sheets and forms a cushion which provides for the slippage between the two sheets as the block 28 is unstacked.

An apparatus embodying the invention provides automatic accommodation for a condition almost certain to exist in stacks of sheets of material such as paper. Even though the manufacturing processes may be carefully controlled, very small variations in the thickness of an individual sheet of paper from one side to the other are bound to occur. Because a stack of paper 25 may consist of as many as, say, 10,000 to 20,000, or more, sheets, if the variation in thickness of a single sheet is even as little as .0001 inch, there may be a difference of as much as two or three inches in the height of the stack at its sides or center. In order to accommodate such variations in the height of the stack 25 throughout its width, the slide 37 provides for relatively free vertical movement of the pusher frame 39 and, as illustrated in FIG. 5, the slide 37 and pusher frame 39 move up and down on the guide angle 34 as the pusher mechanism 16 moves across the stack 25. Similarly, when the separator 15 is inserted between the block 28 and stack 25 it is flexible along its length allowing it to lie closely adjacent the uneven surfaces of the stack 25 and not to bridge any depressions therein so that hollows which would be caused by such a bridging action and would result in the pocketing of air flowing from the nozzle 57, do not exist and the air flowing out of the nozzle 57 is thus useful in providing a cushion of flowing of air throughout the area of the adjacent sheets. The surfaces of the pieces of material 59 and 60 may be waxed, for example, with paraflin or beeswax, not to an extent sufficient to block the openings between the threads but to a degree to lubricate the high spots of the fabric in order to further reduce friction which would otherwise resist the movement of the block 28 over the surface of the stack 25.

I claim:

1. Apparatus for the repetitive unstacking and delivery of blocks of thin, flexible sheets of material such as paper off of the top of a stack of sheets that comprises a plurality of blocks of sheets, said apparatus comprising, in combination, a horizontal table mounted at a fixed level and leading to a subsequent block receiving means, said table having a near on-side and a far off-side, an elevator adjacent the on-side of said table, said elevator being adapted to support and vertically move such a stack of sheets, means for controlling the upward movement of said elevator including an adjustable stop means for limiting each upward movement to a step equal to the height of a block of sheets to be unstacked, a horizontal guideway extending across said elevator from the side thereof remote from said table to the on-side of said table, a block pusher reciprocable along said guide-way and having means for engaging only the upper outer corner and the edges of less than all of the sheets of a block of sheets, separator means for distributing air under pressure between a block of sheets to be unstacked and the lower remainder of said stack of sheets to reduce friction therebetween before movement of said pusher into engagement with said block of sheets, and power mechanism for moving said pusher along said track into engagement with said block of sheets and for moving said block of sheets off of said stack and onto said table.

2. Apparatus according to claim 1 in which said power mechanism includes means for accelerating the rate of movement of said pusher and said block at a selected point in the travel thereof for imparting sufficient velocity to said block of sheets for sliding said block beyond the limit of the movement of said pusher.

3. Apparatus according to claim 1 in which the pusher consists of a generally horizontal plate for engaging the upper surface of a block of sheets and a generally vertical plate normal thereto, said plates forming a right angle adapted to embrace the upper outer corner of a block of sheets and to engage the edges of less than all of the sheets of said block of sheets and means mounting said plates for free vertical movement whereby said pusher plates move vertically and remain in contact with the upper surface of the corner of said block of sheets with substantially uniform pressure to follow a non-planar surface on the upper surface of said stack of sheets.

4. Apparatus according to claim 4 and means for locking said vertical pusher plate with its lower edge extending below said horizontal pusher plate a distance less than the thickness of a block of sheets.

5. Apparatus according to claim 3 in which said means for mounting said pusher plates for vertical movement includes a vertical guide, a slide movable on said guide, means for pivotally mounting said pusher plates at their upper ends on said slide and resilient means urging the lower end of said pusher plates away from vertical toward the block of sheets to be separated, whereby the lower end of said vertical plate first engages the edge of said block upon movement of said pusher and said horizontal plate swings down into engagement with the top of said block E as said pusher plates pivot against said resilient means toward vertical position:

6. Appaiatus for the repetitive un'stacking and delivery of'bloeks' of sheets of material such as paper off of the topof a stack of sheets that comprises a plurality of blocks of sheets, said apparatus comprising, in combination, a horizontal table mounted at a fixed level and leading to ajs'ubsequen't block receiving means, said table having a near oil-side and a far oil-side, an elevator adjacent the ori-sid'ofsaid table, said elevator being adapted to suppo rt and verticallymove such a stack of sheets, said table having a horizontally rnovable section at its on-side adapted to he slid into adjacency with theside of a stack of sheets on said elevator, means for controlling the upward movement of said elevator including an adjustable o ans or l mit n as u w r em to a t equal to theheight of a block of sheets to be unstacked, an overhead track extending, across above said elevator from the side thereof remote from said table to the one side of: said table, a carriage movable along said track, adepending'ar'm on said table, a vertical guide on said arm, a slide movable vertically on said guide, a pusher member pivotally mounted on said guide, said pusher mernjber comprising a vertical plate extending downwardly from said pivotal mounting and a horizontal plate extending toward the stack of sheets, resilient means urging said pusher member pivotally away from vertical toward said stack of sheets, pneumatic mechanism mounted adjacent said track for moving said carriage along said track and control means engageable by said carriage at a point generally central of said track for sharply increasing the rate of movement of said carriage during its feeding stroke. i

7. Appa'r atus for the repetitive unstacking and delivery ofblocks of thin, flexible sheets of material such as paper oitof thetop of a stack of sheets that comprises a plurality of blocks of sheets, said apparatus comprising, in combination; a horizontal table mounted at a fixed level and leading to a subsequent block receiving means, said table having] a near oniside and a far cit-side, an elevator adjacent the oil-side of said table, said elevator being adapted to support and verticallymove such a stack of sheets, means for controllingthe upward movement of said elevator'includin'g' an adjustable stop means for limiting each said table to the o'n-s'ide of said table, a' block pusher reciprocable along said guide-way and having means for engaging only the upper outer corner and the edges less than all of the sheets of a block of sheets, separator means insertable between a block of sheets to be unstackd and the lower remainder of said stack of sheets before movement of said pusher into engagement with said block of sheets and power r'nechanisr'n for moving said pusher along said track into engagement with said block of sheets and for moving said block of sheetsoif of said stack and onto said table, said pusher consisting of a generally horizontal plate for engaging the upper surface of a block of sheets and a generaily'vertical plate normal thereto, said plates forming a right angle adapted to embrace the upper outer corner of a block of sheets and to engage the edges of less than all of the sheets of said block of sheets and means mounting said plates for free vertical movement whereby said pusher plates move vertically and remain in contact with the upper surface of the corner of said block of sheets with substantially uniform pressure to follow a non-planar surface on theupp'er surface of said stack of sheets, said separator means comprising a thin, elongate member having generally flat top and bottom Walls, said walls being porous for exuding air, tlie edges of said member being closed and the end of said member being open, said walls and said member being relatively stiff acros'stheir width and relatively flexible along their length, and an air hose connected to said member for delivering air under pressure thereto.

References Cited in thefile of this patent I UNITED STATES PATENTS 2,076,186 Reynolds Apr. 6", 1937 2,467,493 Pabich Apr. 19, 1949 2,774,489 Gui'gas 2 Dec. 18, 1956 2,854,150 Shea 2 Sept. 30, 1958 2,988,236 Shields Jan. 13, 1961 FOREIGN PATENTS" I 1,013,156 Germany Aug; 1, 1957 

1. APPARATUS FOR THE REPETITIVE UNSTACKING AND DELIVERY OF BLOCKS OF THIN, FLEXIBLE SHEETS OF MATERIAL SUCH AS PAPER OFF OF THE TOP OF A STACK OF SHEETS THAT COMPRISES A PLURALITY OF BLOCKS OF SHEETS, SAID APPARATUS COMPRISING, INCOMBINATION, A HORIZONTAL TABLE MOUNTED AT A FIXED LEVEL AND LEADING TO A SUBSEQUENT BLOCK RECEIVING MEAANS, SAID TABLE HAVING A NEAR ON-SIDE AND A FAR OFF-SIDE, AN ELEVATOR ADJACENT THE ON-SIDE OF SAID TABLE, SAID ELEVATOR BEING ADAPTED TO SUPPORT AND VERTICALLY MOVE SUCH A STACK OF SHEETS, MEANS FOR CONTROLLING THE UPWARD MOVEMENT OF SAID ELEVATOR INCLUDING AN ADJUSTABLE STOP MEANS FOR LIMITING EACH UPWARD MOVEMENT TO A STEP EQUAL TO THE HEIGHT OF A BLOCK OF SHEETS TO BE UNSTACKED, A HORIZONTAL GUIDEWAY EXTENDING ACROSS SAID ELEVATOR FROM THE SIDE THEREOF REMOTE FROM SAID TABLE TO THE ON-SIDE OF SAID TABLE, A BLOCK PUSHER RECIPROCABLE ALONG SAID GUIDE-WAY AND HAVING MEANS FOR ENGAGING ONLY THE UPPER OUTER CORNER AND THE EDGES OF LESS THAN ALL OF THE SHEETS OF A BLOCK OF SHEETS, SEPARATOR MEANS FOR DISTRIBUTING AIR UNDER PRESSURE BETWEEN A BLOCK OF SHEETS TO BE UNSTACKED AND THE LOWER REMAINDER OF SAID STACK OF SHEETS TO REDUCE FRICTION THEREBETWEEN BEFORE MOVEMENT OF SAID PUSHER INTO ENGAGEMENT WITH SAID BLOCK OF SHEETS, AND POWER MECHANISM FOR MOVING SAID PUSHER ALONG SAID TRACK INTO ENGAGEMENT WITH SAID BLOCK OF SHEETS AND FOR MOVING SAID BLOCK OF SHEETS OFF OF SAID STACK AND ONTO SAID TABLE. 